There may be no single cause of bipolar disorder (aka manic depression). Instead, research indicates the causes of bipolar disorder are probably a combination of biochemical, genetic and environmental factors that may trigger and perpetuate the chemical imbalances in the brain.
Net worth: $829 million. Telecommunications mogul Strive Masiyiwa is widely regarded as the richest man in Zimbabwe and is one of the richest men in Africa with a net worth of more than US$800 million.
Bill Gates topped Forbes' richest billionaires list for the third year in a row. With a net worth of $75billion, the Microsoft head has hit the top spot 17 times out of the last 22 years. Zaraâs Amancio Ortega, Warren Buffett and Mexicoâs Carlos Slim Helu came in second, third and fourth, respectively.